Downhole Seismic Source Generator Dynamic Performance Simulation And Structural Optimization

Offshore oil development is based on jacket platform with limited operating space.Cluster Wells are usually used as the main well type,which feature is large number of wells and small distance between wells.The well group arrangement in new oilfield or the well group infill adjustment in old oilfield may collide with each other.Once the borehole collision will bring huge economic losses,so it is very important to provide effective measures for anti-collision monitoring in adjacent wells.With the increase of the borehole depth,the seismic shock intensity generated by the drilling tool becomes more and more difficult to extract effective signals due to the attenuation of the formation medium and the attenuation of the drill string propagation.It is not conducive to anti-collision,so a kind downhole seismic source generator that can provide strong impact strength and operate conveniently was developed.In normal operation,the drilling fluid can be used to store energy for the power equipment without vibration.When measurement distance is needed,the function of ideal impact force can be easily obtained by drilling fluid energy storage and freeing point to remove and so on.The tool can provide effective measures for anti-collision monitoring in adjacent wells.The downhole source generator eliminated the method of spring energy storage through lifting the drill pipe by a large margin,it was designed to adopt mechanical principle for shocking,high-pressure drilling fluid was utilized to store energy,the spring element was utilized as the energy storage mechanism,the steel ball was used as retaining mechanism and hydraulic delay device was to delay.It established hammer’s mechanical model based on the continuity equation of fluid,Bernoulli equation,water resistance and the pressure loss law and so on.A numerical simulation program was built and the differential equation of the velocity,acceleration and displacement on time is solved based on the hammer’s mathematical model by using MATLAB GUI program.So it could estimate the output performance of the downhole seismic source generator;Then it established hammer’s channel model of the downhole seismic source generator.CFD dynamic grid technology was used to simulate the hammer’s working condition,and obtaining the output performance rule.The influence of design parameters on output performance was studied based on single factor analysis and regarding the impact energy of the hammer as the optimization objective,the combination scheme of design parameters was optimized based on the orthogonal experiment method,which selected six factors and three levels and designed 18 sets of experiments.Taking the speed range of the hammer’s output as the critical initial speed of the hammer to carry out the collision simulation of the hammer and anvil,and obtain the output performance data.The study shows that single factor analysis shows that spring stiffness is positively correlated with impact velocity,impact energy and impact efficiency,but negatively correlated with impact displacement;the hammer mass is positively correlated with impact energy,impact efficiency and impact displacement,but negatively correlated with impact velocity;The throttling area,the outlet diameter and the outlet number are positively correlated with the output performance of downhole source generator.The result of orthogonal experiment method shows that the design parameters have different effects on the output performance of downhole source generator.Among all the factors,changing the outlet diameter or spring stiffness has a significant influence on the output performance of the downhole source generator;changing the throttling area,hammer’s mass or outlet number has influence on output performance.On the contrary,changing drilling fluid density has slightly affect.So the best combination scheme of design parameters can be screened out.The simulation results show that the maximum impact speed of the hammer is 3.90m/s,the maximum impact energy is 684.43 J,the impact efficiency corresponding to the maximum impact energy is 88.71%,the maximum impact displacement is 131.59 mm.Impact simulation of impact hammer shows that impact range of hammer is 92.74-241.26 KN,impact energy range of hammer is 111.53-746.60 J,etc.Finally,using theory of strength and ANSYS Workbench finite element analysis software to implement the strength checking and structural optimization of downhole source generator components.The results show that the tool’s structure is reasonable,the output performance can achieve design requirements and it meets actual engineering requirements.